Method for controlling braking force in regenerative brake cooperation control system

Abstract

A method for controlling braking force in a regenerative brake cooperation control system can maximally use regenerative braking force of a rear wheel simultaneously while improving vehicular braking stability by preventing the rear wheel from being locked earlier than a front wheel. The method includes controlling braking forces of the front wheel and the rear wheel by considering a distribution of total vehicular braking force including a coasting regenerative braking force in the regenerative brake cooperation control system in an eco-friendly vehicle which can perform regenerative braking in the rear wheel or both the front wheel and the rear wheel.

What is claimed is: 
     
       1. A method for controlling braking force in a regenerative brake cooperation control system, the method comprising:
 a first step of distributing braking forces of a front wheel and a rear wheel, by a brake controller, so as to generate regenerative braking force for at least one of the front wheel and the rear wheel while vehicle deceleration is less than a reference deceleration while performing braking during coasting driving and distributing rear wheel braking force only up to a rear wheel limit braking force; and 
 a second step of distributing the braking forces of the front wheel and the rear wheel, by the brake controller, according to a set braking force distribution ratio while vehicle deceleration is equal to or more than the reference deceleration. 
 
     
     
       2. The method of  claim 1 , wherein in the first step, only a rear wheel regenerative braking force is controlled to increase at initial braking and the rear wheel braking force constituted by the rear wheel regenerative braking force and coasting regenerative braking force is controlled to increase only up to the rear wheel limit braking force. 
     
     
       3. The method of  claim 2 , wherein in the first step, when the rear wheel braking force reaches the rear wheel limit braking force, the rear wheel braking force is controlled to be maintained to the rear wheel limit braking force and the front wheel braking force is controlled to increase while vehicle deceleration is less than the reference deceleration. 
     
     
       4. The method of  claim 3 , wherein in the first step, in a case of the braking force distributed to the front wheel, only the front wheel regenerative braking force is controlled to increase up to a maximum front wheel regenerative braking force, and thereafter, a front wheel friction braking force is controlled to increase while vehicle deceleration is less than the reference deceleration. 
     
     
       5. The method of  claim 1 , wherein in the first step, the rear wheel braking force is controlled to be maintained as a coasting regenerative braking force, and only the front wheel braking force is controlled to increase while vehicle deceleration is less than the reference deceleration. 
     
     
       6. The method of  claim 5 , wherein in the first step, in a case of the braking force distributed to the front wheel, only a front wheel regenerative braking force is first controlled to increase, and thereafter, a front wheel friction braking force is controlled to increase. 
     
     
       7. The method of  claim 5 , wherein the rear wheel limit braking force of the first step has a same value as the coasting regenerative braking force. 
     
     
       8. The method of  claim 1 , wherein in the first step, the rear wheel braking force is controlled to be maintained as a coasting regenerative braking force at initial braking and only a front wheel regenerative braking force is controlled to increase while vehicle deceleration is less than a first deceleration having a smaller value than the reference deceleration. 
     
     
       9. The method of  claim 8 , wherein only the rear wheel braking force is controlled to increase while vehicle deceleration is equal to or more than the first deceleration and is less than a second deceleration and the second deceleration has a value larger than the first deceleration and smaller than the reference deceleration. 
     
     
       10. The method of  claim 9 , wherein in a case of the braking force distributed to the front wheel, while vehicle deceleration is equal to or more than the first deceleration and less than the second deceleration, only the front wheel regenerative braking force is distributed to be maintained as a maximum front wheel regenerative braking force. 
     
     
       11. The method of  claim 10 , wherein while vehicle deceleration is equal to or more than the second deceleration and less than the reference deceleration, the front wheel regenerative braking force is controlled to be maintained as the maximum front wheel regenerative braking force and only a front wheel friction braking force is controlled to increase. 
     
     
       12. The method of  claim 9 , wherein while vehicle deceleration is equal to or more than the first deceleration and less than the second deceleration, in a case of the braking force distributed to the rear wheel, only the rear wheel regenerative braking force is controlled to increase, and the rear wheel braking force constituted by the rear wheel regenerative braking force and the coasting regenerative braking force is controlled to increase only up to the rear wheel limit braking force. 
     
     
       13. The method of  claim 12 , wherein when the rear wheel braking force reaches the rear wheel limit braking force, the rear wheel braking force is maintained as the rear wheel limit braking force while vehicle deceleration is equal to or more than the second deceleration and less than the reference deceleration. 
     
     
       14. The method of  claim 1 , wherein in the second step, in a case of the braking force distributed to the rear wheel, a rear wheel regenerative braking force increases up to a maximum rear wheel regenerative braking force, and thereafter, the rear wheel regenerative braking force is controlled to be maintained as the maximum rear wheel regenerative braking force and only a rear wheel friction braking force is controlled to increase. 
     
     
       15. The method of  claim 1 , wherein in the second step, in a case of the braking force distributed to the front wheel, a front wheel regenerative braking force is controlled to be maintained as a maximum front wheel regenerative braking force and only a front wheel friction braking force is controlled to increase. 
     
     
       16. The method of  claim 1 , wherein in the second step, the front wheel braking force is distributed as a value of “T d *C F /(C F +C R )+T 1 *C F /(C F +C R )” and the rear wheel braking force is distributed as a value of “Td*C R /(C F +C R )−T 1 *C F /(C F +C R )+T 1 ”,
 wherein Td represents a driver required braking force, T 1  represents a coasting regenerative braking force, C F /(C F +C R ) represents a front wheel braking force rate depending on a braking force distribution ratio of a distribution line, and C R /(C F +C R ) represents a rear wheel braking force rate depending on the braking force distribution ratio of the distribution line.